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Proceedings Paper

Instantaneous speckle reduction? Yes, but there is no free lunch!
Author(s): Gerd Häusler; Florian Dötzer; Klaus Mantel
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Paper Abstract

We are motivated by the question if scanning laser projection with low speckle noise is possible. Scanning laser projection requires “instantaneous” speckle reduction, within a few nanoseconds – meaning that no moving diffusors can be used. We will argue that instantaneous speckle reduction is possible by conversion of spatial coherence to spatial incoherence - but nature demands for a compensation. The cost can be estimated via the information theoretical concept “channel capacity”, which incorporates the etendue as well as the signal-to-noise ratio. We will show that an optical system with low spatial coherence (=low speckle noise) must provide significantly more degrees of freedom than a coherent imaging system. The consequence for the technical optical system is serious: significant speckle reduction can only be achieved by an excessively large projection aperture. This is not just a sophistic consideration, it seriously restricts the design of scanning laser projectors.

Paper Details

Date Published: 7 September 2018
PDF: 7 pages
Proc. SPIE 10834, Speckle 2018: VII International Conference on Speckle Metrology, 108340B (7 September 2018); doi: 10.1117/12.2317925
Show Author Affiliations
Gerd Häusler, Friedrich-Alexander-Univ. Erlangen-Nürnberg (Germany)
Florian Dötzer, Friedrich-Alexander Univ. Erlangen-Nuremberg (Germany)
Klaus Mantel, Max-Planck Institute for the Science of Light (Germany)

Published in SPIE Proceedings Vol. 10834:
Speckle 2018: VII International Conference on Speckle Metrology
Malgorzata Kujawińska; Leszek R. Jaroszewicz, Editor(s)

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